The present invention relates to a system that checks whether or not any errors are present in data signals that have been transferred serially from one electronic cash register to another cash register.
Conventionally, when data signals are transferred from one electronic cash register (hereinafter referred to as "ECR") to another ECR, the data-transmitting register of the transmitting ECR serially transfers data signals to the data-receiving register of the receiving ECR. These conventional transmitters must check whether or not the data has been received correctly. This error check is executed in accordance with the procedure described below. After the initial data transfer, the receiving ECR sends back the received data to the data-receiving register of the initial transmitting ECR. The data-transmitting register of the initial transmitting ECR then compares this data with the originally transmitted data. Thus, the error-checking system employed by any such conventional ECR system must transfer the data twice, first in one direction and then back in the other direction. This error checking system inevitably doubles the time required for simple data transfer without error checking.